The article is devoted to the analysis of some aspects of the study of the arboreal flora of Dagestan. It assesses the taxonomic richness (306 species, 105 genera and 51 families) and life forms (trees – 57 species, shrubs – 210, shrubs –5, lianas –5, semi-shrubs – 29), discusses the problem of finding and identifying tree species new to the territory of the Republic and assessing the status of some species that successfully grow in various natural environments. communities, but not yet classified as natural flora.

The article summarizes data from 1931 to 2021 on anthropogenic transformation and dynamics of forest cover in Dagestan, which currently amounts to approximately 10,6%. In order to remove contradictions in the estimation of the number of tree species and in order to unify common approaches to the assessment of forest vegetation, some generally accepted terms and concepts are discussed. The problems of the nomenclature status of species of the genera Rosa, Crataegus, Quercus, Salix and the need for additional studies on 30 species to confirm their species status using molecular genetic methods are outlined.

The role of some alochthonous tree species in the formation of distinctive communities is evaluated. On the territory of Dagestan, one of these species is Armeniaca vulgaris Lam., which forms unique natural monodominant communities and landscapes on significant areas of the slopes of the Inland Dagestan.

The modern approaches and methods used to identify the real area of forests on mountain slopes are characterized, the existing problems and errors are noted here.

The main purpose of this work was to identify a possible way of speciation of the Caucasian endemic R. oxyodon Boiss. In this regard, an attempt was made to study the genetic relationships of R. oxyodon with related species R. pendulina, R. majalis, and R. donetzica by sequencing the sequence of the trnL-trnF chloroplast spacer. The sample size for chloroplast DNA analysis was 48 samples. DNA isolation was carried out by the STAB method from dried leaves. In all studied samples, the sequence of the chloroplast intergenic spacer trnL-trnF was sequenced. The sequenced sequences of the trnL-trnF chloroplast spacer were manually aligned using the BioEdit v7.0.5 program. Data analysis was carried out using the statistical parsimony method implemented in the TCS v. 1.21. The analysis included 83 sequences. The alignment length was 293 positions. As a result of the work done, 18 haplotypes were identified, 7 of which were absent among the samples and were hypothetical extinct. The remaining haplotypes were distributed as follows: 1) R. pendulina: A, B, C, D, E; 2) R. majalis: F, L, M; 3) R. oxyodon: A, F, G, H, I; 4) R. donetzica: E, F.

R. oxyodon is characterized by haplotypes A and F, genealogically distant from each other and occurring in R. pendulina, R. majalis, and R. donetzica, respectively. Such a distribution of haplotypes in the three species under consideration, including disjunctions in the distribution of haplotype A, suggests the hybrid origin of R.oxyodon as a result of multiple reciprocal (at least two) hybridizations between R. pendulina and R. majalis.

The accumulated data on the distribution and ecological preferences of 4 vulnerable moss species Grimmia laevigata, Eucladium verticillatum, Gymnostomum aeruginosum, Fontinalis antipyretica are summarized. All species have low occurrence and single points of growth. Limiting factors: natural (low competitive ability, narrow ecological amplitude, rare occurrence, low density and population size) and anthropogenic (economic activity, tourism).

Data on the coenoflora of forests dominated by Betula litwinowii and Betula raddeana in the tree layer in Alpine and Inland Dagestan based on the results of field studies 2018–2020 are presented. 103 geobotanical descriptions were performed in the Gunibsky, Charodinsky, Tsumadinsky, Laksky, Akushinsky, Tsuntinsky and Dokuzparinsky administrative districts. The total number of vascular plant species in the communities described by us is 438, of which 18 are in the tree stand, 32 are in the undergrowth layer, and 388 are in the grass-shrub layer. The species of the coenoflora of the birch forests belong to 73 families, 219 genera. The order of distribution of the leading 10 families of the coenoflora of the birch forests of Dagestan characterizes it as typical for the flora of the Holarctic kingdom. The presence of Poaceae in second place in the number of species, after Asteraceae, as well as the abundance of Ranunculaceae species (3,19%) reflect the boreal features of the coenoflora of the birch forests of Dagestan. The biomorphological spectrum is dominated by hemicryptophytes (70,32%), which is characteristic of mountain flora and also indicates the Holarctic nature of the flora. Moss-lichen layer and undergrowth of birch forests, as a rule, are poorly developed except for communities with undergrowth of Rhododendron caucasicum, the projective coverage of which reaches 90%. In the grass-shrub layer of birch forests, meadow species predominate (46,58%). Most of the dominants of the grass-shrub layer are meadow subalpine species.

New data on the rare and endangered East-Mediterranean species Sorbus kusnetzovii are presented. An ecological and geographical characteristic of new localities are given with characterization a participation of the species in phytocenosis. The primary results of species growth at the experimental bases of the Mountain Botanical Garden are given.